Environ. Sci. Techno/. 1995, 29, 2133-2139
DDT, a Potential Source of Tris(4chloronhenvl)methane and HANS-RUDOLF BUSER Swiss Federal Research Station, CH-8820Wiidenswil, Switzerland
Tris(4-chlorophenyl)methane (4,4’,4”-TCPM) and its presumed metabolite tris(4-~hlorophenyl)rnethanol(4,4’,4”TCPM-OH) are among the most recently identified organochlorine contaminants in environmental biological samples. The compounds are present on a global scale and found in samples from practically all continents. Initially discovered in various aquatic species, they have now also been detected in human milk. However, despite of their widespread occurrence, the source and the origin of these compounds are so far unknown. In this study, we report the first evidence of a link between environmental TCPM and DDT. 4,4’,4”-TCPM and two additional isomers, 2,2’,4”- and 2,4‘,4”-TCPM, were formed in small amounts from the reaction of chloral, chlorobenzene, and fumic sulfuric acid under conditions such as those used in the technical synthesis of DDT. The same TCPM isomers were also detected in two samples of technical DDT, one more than 40 years old. In environmental biological samples, particularly at higher trophic levels, generally just a single isomer of TCPM and TCPMOH is present; the latter was previously identified as the 4,4’,4”-isomer, and the same isomerism is now confirmed for the former. Preferred degradation of the isomers with 2-chloro rings in metabolic actions presumably is the reason for the absence of other isomers in biological samples. All 10 possible TCPM isomers were formed in a novel reaction of DDT with chlorobenzene in the presence of AIC13. They were completely resolved by high-resolution gas chromatography and assigned from retention and mass spectrometric data.
Introduction Among the most abundant organochlorine contaminants in the environment are the hexachlorocyclohexanes(HCHs), DDT (1,1,l-trichloro-2,2-bis[4-chlorophenyl] ethane) and related compounds, and polychlorobiphenyls (PCBs). Just a few years ago, a new compound, tris(4-chloropheny1)methanol (4,4’,4”-TCPM-OH) (see Chart 11, was detected (1). TCPM-OH was first discovered in harbor seals from the northwestern United States (I),and its occurrence was
OOl3-936)(/95/0929-2133$09.00/0
D 1995 American Chemical Society
correlated with most other organochlorine contaminants like DDT, PCBs, and dieldrin. Since then, 4,4‘,4“-TCPMOH and its presumed precursor tris(4-dhloropheny1)methane (4,4’,4”-TCPM;see Chart 1)were detectedin ringed seals from the Baltic Sea (2) and in sea birds and sea mammals throughout North America and elsewhere in both the Northern and the Southern Hemispheres (3). Both compounds have now also been detected in human milk (4). TCPM-OH seems to be present in the environment since more than 40 years ago (3). No sources of TCPM and TCPM-OH have been identified so far. Though TCPM is structurally related to DDT and TCPM-OH is related to dicofol (l,l,l-trichloro-2,2-bis[4chlorophenyllethanol), this relationship was not proven. On the contrary, the absence of detectable (20.1%)quantities of TCPM-OH in a sample of technical DDT and in a sample of dicofol was reported (I). Previous literature searches revealed several citations for TCPM, TCPM-OH, and related compounds (I,3). From citations in the patent literature, the uses of such compounds in synthetic (optically active) high polymers and for lightfast dyes for acrylic fibers were suggested as sources for environmental TCPMOH (3). However, some of this patent literature is rather new, and it is questionable whether these uses would account for the apparently long-time presence of TCPMOH in the environment. In this paper, we present the first evidence for a link between environmental TCPM and DDT. We show that under certain conditions all the theoreticallypossible TCPM isomers are formed from DDT with chlorobenzene in the presence of condensing reagents. We also report that 2,2’,4“-, 2,4’,4”-, and 4,4’,4”-TCPM are formed from l,l,ltrichloroacetaldehyde(chloral)and chlorobenzene in reactions such as those used in the synthesis of DDT, and we document the presence of the same isomers in two commercial samples of DDT.
Experimental Section Materials and Reference Compounds. Two samples of technical DDT were from Promochem (Wesel, Germany) and from Maag (Dielsdorf,Switzerland),respectively. The latter sample was obtained in the 1950s and has been archived in Wadenswil. Both samples were recently analyzed and showed a typical composition for technical DDT with ~ 7 9 %4,4‘-DDT, 16-18% 2,4‘-DDT, and other compounds (5). Solutions in n-hexane at concentrations of 100-1000 nglpL were analyzed. Analytical grade 2,4’DDT and 4,4’-DDT were from Promochem. Chloral, chlorobenzene, fumic and concentrated sulfuric acid, and anhydrous AIC13 and FeCb were from Fluka (Buchs, Switzerland). Biological Sample Analyzed. Composite (pooled) adipose tissues of adult ringed seal (Phocu hispiah) collected from the Baltic Sea along the Swedish eastern coastline were examined. The samples were prepared at the Institute of Environmental Chemistry, University of Umei, Sweden (courtesyD. Zook and C. Rappel for use in an earlier study (2).In the study here, the Florisil fraction 2 was analyzed. Preparation of TCPM Isomers from the Reaction of DDT with AlC& in Chlorobenzene. This reaction was typically carried out as follows: x10 mg of anhydrous dC13
VOL. 29, NO. 8,1995 I ENVIRONMENTAL SCIENCE &TECHNOLOGY 12133
CHART 1
4,4',4"-TCPM
4,4',4"-TCPM-OH
was placed into a 2-mL ampule and covered with 300 pL of chlorobenzene. This mixture was frozen with dry ice. Then, 100 pL of a solution containing 25 mg of technical DDT, 2,4'-, or 4,4'-DDT in chlorobenzene was added. The contents of the ampule were then quickly frozen again, and the ampule was flame-sealed under vacuum. The ampule was then slowly warmed by hand to melt its contents. Under shaking, the initially colorless mixture slowly turned red, purple, and finally to a deep dark color. Under occasional shaking, the contents were reacted at room temperature (rt) or were heated for 60 min to 40-45 "C for optimum formation of TCPMs and occasionally to higher temperatures (100 "C). After the reaction, the contents of an ampule were frozen again, and the ampule was opened. After melting, the deeply colored mixture was brought into a 20-mLvial by pipet. About 3 mL of n-hexane was added, and then 2 mL of distilled water to decompose AlC13 was added. Mixing of the two phases was achieved by pumping action with the pipet. The color of the organic phase changed to a deep yellow-orange. The aqueous phase was discarded, and the organic phase was washed at least four times with small portions of distilled water until neutral. The organic phase was then passed through a small silica column (0.7 g of silica gel 60, Merck, Darmstadt, Germany; 5 mm i.d. Pasteur pipet) topped with Na2S04. TCPMs were eluted with 10 mL of 20% methylene chloride in n-hexane. All 10 TCPM isomers and DDT were completely eluted into this fraction. The eluate typicallyshowed an intense yellow color and contained various TCPM isomers in high concentration. Suitable dilutions in n-hexane were used for gas chromatographylmass spectrometric (GUMS)analysis. Appropriate blank reactions without DDT or AlC4, respectively,were carried out accordingly. Allvials were wrapped with aluminum foil to protect the solutions from exposure to light. LaboratoryPreparation of DDT. DDT was prepared in the laboratory as follows: a mixture of 5.0 g of chloral and 11.5 g of chlorobenzene was prepared (molar ratio, 1:3).To 4 g of this mixture in a 20-mL vial was slowly added 3 g of fumic sulfuric acid dropwise under gentle agitation (rotation of the vial) (molar ratio fumic sulfuric acidlchloral 4:l). The mixture was kept handwarm, and no cooling was applied. The complete addition took 20-30 min. After each drop of fumic H2S04, the mixture became reddish and then changed to orange. On standing, two layers formed. About one-third of the mixture was slowly added to 50 mL of water. Solid NaHC03was carefully added until CO2 production ceased. The mixture was then extracted with three portions of diethyl ether (50 mL total), and the extracts were combined and dried with anhydrous Na2S04. A 0.22134
ENVIRONMENTAL SCIENCE &TECHNOLOGY / VOL. 29, NO. 8, 1995
mL aliquot was then passed through a small silica column (see above), and DDT and byproducts were eluted with 10 mL of 20%methylene chloride in n-hexane. A small aliquot (1 pL) of 10-fold dilution was analyzed by GCIMS. The reactions were also carried out with concentrated sulfuric acid in place of fumic H2SO4 and using magnetic stirring in place of hand swirling. Again, appropriate blanks were run (see above). High-Resolution Gas Chromatography (HRGCVMS Analysis. A VG Tribrid double-focusing magnetic sector mass spectrometer (Fisons-VG,Manchester, England) was used. The ion source was operated under electron ionization (EI, 70 eV, 180 "C) conditions. Full-scan E1 mass spectra (mlz 35-535, 1.16 slscan, resolution MIAM = 500) were recorded for analyte identification. Analyses were also carried out with selected ion monitoring (SIM,cycle times, 0.5 slscan) by using ions at mlz 346, 348, 311, and others to detect TCPMs and at mlz 352, 354, and 235 to detect DDT; a lock mass of mlz 207.033 from the silicone bleed of the HRGC column was used. Total concentrations of TCPMs relative to DDT were determined by comparison of peak areas from mass chromatograms mlz 346 and 352 (TCPMs and DDTs, respectively; all isomers summed), corrected for the relative abundances (ra) of these ions in the E1 mass spectra (5%and 0.3% ra for TCPMs and DDTs, respectively), and assuming the same response for isomers. The data thus generated are semiquantitative, and quantitation was not of prime concern in this study. The samples were analyzed using a 25-m SE54 fused silica (0.32mm i.d.1 HRGC column (MEGA, Legnano, Italy), temperature programmed as follows: 50 "C, 2-min isothermal, 20 "Clmin to 160 "C, then at 2 "Urnin to 280 "C, followed by an isothermal hold at this temperature. Oncolumn injection (1 pL) in n-hexane was used. Data acquisition was started at 160 "C.
Results and Discussion Formation of TCPM Isomers from the Reaction of DDT with Chlorobenzene in the Presence of AlCls. When technical DDT, 2,4'-, or 4,4'-DDT was dissolved in chlo-
robenzene and some anhydrous AlC13 was added, the solution quickly changed its color from colorless to a deep purple with some production of gas (HC1). A similar reaction was observed with DDT in benzene in the presence of AlC13. This reaction was previously observed (6),apparently used as a colorimetric method to determine DDT, but the reaction products were not identified. When this reaction was carried out with technical DDT at 45 "C as described in the Experimental Section,the eluate from the silica column analyzed typically showed a distinct yellow color. The major products ('50%) in this fraction were various TCPM isomers. In Figure 1, we show a GC/ MS chromatogram of this reaction mixture. The peaks observed (in order of their elution) were bis(chloropheny1)methanes (Me+= mlz 236, Clz; retention time 5.1-6.7 min; six isomers), l,l-dichloro-2-(2-chlorophenyl) -244chloropheny1)ethene (2,4'-DDE; M + = mlz 316, C&; retention time 13.3 min), TCPM isomers (M" = m/z 346, C13; retention time 23-32 min; 10 isomers), and compounds tentatively identified as tris(chloropheny1)ethenes ( M + = mlz 358, C13; retention time 33-36.5 min; three isomers), trichloro-9-phenylphenanthrene( M + = m/z 356, C13; retention time 47.0 min), and tetrachloro-9,lO-diphenylphenanthrenes ( M + = mlz 466, C14;retention time 63.5-
TABLE 1
TCPM Isomers from the Reaction of DDT with Chlorobenzene in the Presence of AlCll peak no.'
1o:oo
FIGURE 1. GC/MS (m/z35-535) chromatogram of the products from the reaction of technical DDT with chlorobenzene in the presence of AICL (45 OC). Peak identifications (see text): 1-6, bis(chloropheny1)methenes; 7,2,4'-DDE 8-17, TCPM isomers: 18-20, tris(chloropheny1)ethenes; 21, trichloro-9-phenylphenanthrene (tentative); 22-23, tetrachloro-9.10-diphenylphenanthrenes(tentative).
isomer assignment
1 2 3 4 5 6 7 8 9 10
isomer typeb
I I I I I I1 I II II I1
2,2',2"-
2,2',32,2',4"2,3',32,3',4"3,3',32,4',4"3,3,4"3,4',4"4,4', 4"-
elution temp ("C)" 206.15 209.95 212.15 213.45 215.7 217.1 5 217.85 219.35 221.6 223.8
aPeak numbers refer to Figure 2. bType I and type II isomers from El mass spectra with ratios [m/z 2351/1m/z 2391 < l and >1, respectively. Elution temperatures on SE54, for conditions see text; elution temperatures for 2,4'- and 4,4'-DDT were 196.7 and 201.8 "C, respectively.
SCHEME 1
Reaction of DOT with Chlorobenzene in the Presence of AICb8
4,4'-DDT
FIGURE 2. SIM (m/z 346) chromatogram showing elution and resolution of all 10 theoretically possible TCPM isomers formed from the reaction of technical DDT with chlorobenzene in the presence of AlCla (45 O C ) . For lines 1-3, see text. For isomer assignment, see text and Table 1.
67.5 min; two isomers), the latter compounds possibly formed from tris- and tetrakis(chloropheny1)ethenes by hydrogen abstraction (aromatization). No residual DDT was detectable. No TCPMs were formed in the absence of DDT or AlC13. In Figure 2, an E1 SIM (mlz 346) mass chromatogram shows the elution of TCPMs from this reaction mixture. The chromatogram shows the presence of all 10 TCPM isomers, though at different relative abundances. Theoretically, there are 10 TCPM isomers possible (see Table 11, and apparently all were formed under these reaction conditions (isomer assignments, see below). The isomers are completely resolved by the HRGC column. The formation of all TCPM isomers indicated not only substitution of the CC13group in DDT by chlorophenyl but suggested extensive isomerization and exchange of the 4-chlorophenyl(and2-chlorophenyl)substituents from 4,4'and 2,4'-DDT by chlorophenyl from chlorobenzene. This exchange was confirmed when the reaction was repeated with benzene. In this case, tris(pheny1)methane ( M + = m / z244) and some chlorophenyl-bis(pheny1)methane( M + = m / z 278) were among the products, but no bis(chloropheny1)-phenylmethane (M'+ = m / z 312) was formed, the product expected from substitution of CC13 in DDT by phenyl. The results indicated that all three chlorophenyl substituents in the TCPMs are derived from chlorobenzene according to Scheme 1. When this reaction was repeated with technical DDT, 2,4'- or with 4,4'-DDT under milder conditions (rt), fewer TCPM isomerswere observed (see chromatograms in Figure
CI
W-Q CI TCPM (10 isomers)
a See text forthe formation of additional compounds in this reaction. Under certain conditions all the 10 theoretically possible isomers are formed.
3a-c), and DDE was a major product. The TCPM isomers formed from 4,4'- and 2,4'-DDT were now 2,2',4'-, 2,4',4"-, and 4,4',4"-TCPM (for assignments, see below). The formation of 4,4',4"-TCPM from 2,4'-DDT (see Figure 3c) again shows that at least two of the chlorophenyl substituents are derived from chlorobenzene. From technical DDT, a somewhat more complex isomer mixture was obtained (see Figure 3a). When the reaction was carried out at higher temperatures (100 "C), other deeply colored products were formed with little TCPMs remaining. When AlCb was replaced by FeC13,DDE was the major product. Tentative TCPM Isomer Identification from Chromatographic Data The temperature conditions of the GC analyses were chosen in a way that all TCPM isomers eluted well within the linear temperature program of the HRGC analysis. This was achieved with a 2 OClmin rate starting at 160 "C. Under these conditions, all TCPM isomers were eluted between 206 and 224 "C and resolved by the relatively nonpolar SE54 HRGC column. From the retention data of DDT, l,l-dichloro-2,2-bis(chloropheny1)ethane (DDD), and DDE isomers, respectively, it is known that isomers with 4-chloro rings elute last and well after isomerswith 2-chloro rings. We therefore assumed that the last eluting isomer in Figure 2 (isomer 10) was 4,4',4"-TCPM, and the earliest eluting isomer (isomer VOL. 29,
NO. 8, 1995 /ENVIRONMENTAL SCIENCE &TECHNOLOGY 12135
series 1 Isomers (AT1 values 5.410.2 “C)
2.2,r‘
2,2,4“
2,4.4
2,2’,3
3,l
40 30 20
1
10
0
,, ,
:
9
,
,;
, I
, , , , , ,:, , ;
3,4’,4”
0
(AT2 values 2.rn.05 ‘C)
peak number 1
2
1
1
3 I
1
1
I ZC4
ZCd
210
212
5
4 I
6
I I
214
I
216
7
I 1 I
218
8 1
9 1 I
220
I
222
IO I I
224%
elution temperature (SE54)
60
71
50
40 30 20 10 0 ,,,,,
,
10
b
/
2,3,4
6 e r k 3 iromets (AT3 values 3.633.1 5 ’C)
5
2
100 00 70
\
4.4,4”
P
a
”
A
70 60 50
3 , , , , ,
, , , , r A , . - , ,
FIGURE 4. Graphical presentationof the elution temperatures of all 10 TCPMs. Note the about equidistant elutions of isomers in the isomer series 1,2, and 3 (sea text).
9 , , , , ,
,,A,,,
, , , , ,
, , ,
FIGURE 3. SIM (nJz346)chromatogram showing elution of TCPM isomers formed from the reaction of (a) technical DOT, (b) 4,4‘-DDT, and (c) 2,4’-DOT with chlorobenzene in the presence of AICh under milder conditions (room temperature). Note formation of fewer isomers. For isomer assignment, see text and Table 1.
1)was 2,2‘,2”-TCPM. The former assumption is supported by the fact that isomer 10 is the one present in environmental samples (see below), and its presumed metabolite was independently identified as 4,4’,4’’-TCPM-OH (1-3). A first series of isomers can be expected from the consecutive replacement of each 4-chloro ring by a 2-chloro ring in4,4’,4”-TCPM, Ina first approximation, it can be assumed that each such replacement is accompanied by a constant change in retention time (or elution temperature). These assumptions would suggest an elution of isomers in an ascending order such as 2,2‘,2’’- < 2,2’,4”-< 2,4’,4”- < 4,4’,4’TCPM and elution at about constant retention time or elution temperature increments (AT) in a temperatureprogrammed run. An inspection of the chromatogram in Figure 2 revealed isomers 1, 3, 7, and 10 eluting at about constant retention increments (noteline 1in Figure 2) with ATl values of 5.95, 5.70, and 6.00 “C (mean 5.9 f 0.2 “C), respectively. These values are similar to the one between 4,4’- and 2,4’-DDT (AT= 5.1 “C, see Table 1). From these considerations, isomers 1, 3, 7, and 10 were tentatively identified as 2,2‘,2”-, 2,2’,4“-, 2,4‘,4”-, and 4,4’,4“‘-TCPM, respectively. Note that for this series the relative abundance of the midrange isomers (isomers 3 and 7) is larger than that of the border isomers (isomers 1 and 10). Isomers 3, 7, and 10 were those formed under the mildest conditions from 2,4’- and4,4’-DDT (see Figure 3) and expected to have only 2- and 4-chloro rings. The four isomers tentatively identified in this way exclusivelycontain2- and 4- chloro rings. The sixremaining isomers (isomers 2,4,5,6,8,and 9) therefore must contain 3-chloro rings. Asecond series of isomers can be expected from the consecutive replacement of each 4-chloro ring by a 3-ChlOrO ring in 4,4’,4”-TCPMand suggest their elution 2136 1 ENVIRONMENTAL SCIENCE &TECHNOLOGY / VOL. 29, NO. 8,1995
in an ascending order such as 3,3‘,3”- < 3,3’,4“- < 3,4’,4”< 4,4’,4”-TCPM and elution at about constant retention increments. An inspection of the peak elutions in Figure 2 revealed isomers 6,8,9, and 10 eluting at about constant retention increments (note line 2 in Figure 2) with AT2 values of 2.2, 2.25, and 2.2 “C (mean 2.2 f 0.05 “C), respectively. From these considerations isomers 6, 8, and 9 were tentatively identified as 3,3’,3”-,3,3’,4”-,and 3,4’,4”-TCPM, respectively. The relative abundances of the isomers in this series show a similar trend as the series 1 isomers. A third series of isomers can be expected from the consecutive replacement of each 2-chloro ring by a 3-chloro ring in 2,2’,2”’-TCPM and suggest their elution in an ascending order such as 2,2’,2”- < 2,2’,3”- < 2,3’,3”- < 3,3’,3”’-TCPM. An inspection of the chromatogram in Figure 2 revealed isomers 1, 2, 4, and 6 eluting at about constant retention increments (note line 3 in Figure 2) with AT3 values of 3.8, 3.5, and 3.7 “C (mean 3.65h0.15 “C), respectively, the expected difference from the ATvalues of the series 1and series 2 isomers (see graph in Figure 4; note from the abscissa values that ATl = AT2 ATd. Isomers 2 and 4 therefore were tentatively identified as 2,2‘,3“- and 2,3’,3”-TCPM,respectively. Again, the relative abundances of the isomers in this series show a similar trend as the series 1 isomers. The remaining isomer 5 therefore has to be 2,3’,4”-TCPM. This major isomer is eluting at the expected elution temperature (ATvalues relative to neighboring isomers are ATi= 5.9 f O.l”C,ATz= 2.2 f O.O5”C,and AT3= 3.6 h 0.05 “C;see graph in Figure 4). Assuming a similar reactivity at each ortho, meta and para position in chlorobenzene and from statistical considerations, this is one of the major isomers expected. The tentative identifications of all the isomers and their elution temperatures are listed in Table 1 and graphically presented in Figure 4. At least 2,3’,4“TCPM is chiral; other isomers may be chiral due to the propeller-like configuration of these molecules (7). E1 MS Differentiaton of TCPM Isomers. All TCPM isomers showed intense E1 mass spectra with abundant molecular ions (M+) at mlz 346. The major fragment ions were M+ - C1 (mlz 311, base peak for all isomers), M - Cl-HC1 (mlz 275), M + - C1- 2HC1 (mlz 239), M” - CsHdC1 (mlz 235), M’ - CsH4C1- HCl (mlz 199),M’+ - CsH4C1- Clz (mlz 165), and others. Minor fragmentation led to M’ Clz(mlz276) and M’ - Clz- HC1 (mlz240) and their doubly charged analogs (mlz 138 and 120, the latter intense).All ions (where appropriate) show the expected clustering due to the C1 isotopes. The mass spectra of some isomers showed distinct differences among the relative abundances
+
SCHEME 2
3I"1
Fonnation of Technical DDT from the Reaction of Chloral and Chlorobenzene in the Presence of Fumic or Concentrated Sulfuric Acid (Bayer Condensation)
M/Z
THO
cc13
1100% 199 60 50
120
165
346
40
30
4,4'-DDT + isomers + byproducts
20
10 0
The isomers detected were 2,4',4"- and 4,4',4"-TCPM (isomers 7 and 10) and a smaller amount of 2,2',4"-TCPM (isomer 3) at a combined level of %0.5%relative to the amount of DDT present. The preparations containing TCPMs were those obtainedwith gentle agitation (minimum 165 199 stirring). When the reaction was carried out with faster 30 (magnetic)stirring,no TCPMs were formed. Similarily, no 20 TCPMs were detected when the reaction was carried out 10 with concentrated H2SO.I ( 1,inagreementwiththe above isomers showing type I spectra were exclusively thoseidenassignment. An inspection of the mass spectra for envitified with 2-chloro rings, and all those showing type I1 ronmental TCPM reported in other studies (2, 3) also spectra were those without2-chloro rings, according to the indicate type I1 spectra ([mlz 2351 l [mlz 2391 > 1). retention data above. Conclusions Formation of TCPMs from the Reaction of Chloral and In this paper, we give the first evidence for a link between Chlorobenzene Such As Used in the Technical Synthesis environmental TCPM and DDT. Two samples of technical of DDT. Small-scale syntheses of DDT were made from DDT, one produced over 40 years ago, showed the presence the reaction of chlorobenzene with chloral in the presence of small amounts of 4,4',4"-TCPM and of two other isomers, of fumic or concentrated sulfuric acid (seereaction Scheme 2,2',4"- and 2,4',4"-TCPM. DDT prepared in the laboratory 2). The E1 SIM (mlz 346) chromatograms of two preparafrom chloral, chlorobenzene, and fumic sulfuric acid under tions are shown in Figure 6a,b. From the reaction with certain conditions contained the same TCPM isomers. The fumic H2S04, clearly TCPMs are formed (see Figure 6a). failure to establish this linkbefore (seeref 1) likely stemmed The original reaction mixture showed some orange color. 1100%
I
VOL. 29, NO. 8,1995 /ENVIRONMENTAL SCIENCE & TECHNOLOGY
2137
'13 a
:
1:
22:OO
24:OO
26:OO
28:OO
30:OO
32:OO
T ME
FIGURE 7. El SIM ( d z 346)chromatogram of seal adipose tissue showing elution of a TCPM isomer, now identified as 4,4',4"-TCPM (isomer 10). (b) El mass spectrum of the major peak in panel a indicating a TCPM type II isomer.
FIGURE 6. SIM ( d z 346)mass chromatograms showing presence (a, c, and d) and absence (b) of TCPM isomers in (a) laboratoryprepared DDT (fumic sulfuric acid), (b) laboratory-prepared DDT (concentrated sulfuric acid), (c) technical DDT, Promochem, and (d) technical DDT, Maag. Note the presence of2,2',4"- (isomer 3),2,4',4"(isomer 7), and 4,4',4'-TCPM (isomer IO) in one of the Iaboratoryprepared DDTs (a) and in both of the commercial, technical DDTs (c and d).
from the fact that detection levels were high (0.1%),and actually TCPM-OH was searched and not TCPM. As previously pointed out (31, TCPM-OH likely results from hydroxylation of TCPM by metabolic action or by microbiological or direct chemical transformation in the environment. However, TCPM still shows considerable persistence since otherwise it would likelyhave been degraded in the environment. In a novel reaction, DDT was reactedwith chlorobenzene in the presence of anhydrous AlC13. Complex reaction mixtures with all 10 theoretically possible TCPMs were formed under certain conditions and with all chlorophenyl substituents being derived from chlorobenzene. The isomers were fully resolved by HRGC, characterized by E1 MS, and assigned by retention and E1 MS data. Solutions of the synthetic TCPMs were of a distinct yellow color. This color is possibly due to some radical or ion formation. It is known that triphenylmethylradicals are yellow and other triarylmethyl radicals are orange to brown (9). It is also known that some triphenylmethyl compounds form deeply colored salts with mineral acids. Triphenylmethylradicals, in fact, were the first stable free radicals known (9). In the technical production of DDT, chlorobenzene is condensed with chloral in the presence of fumic or concentrated sulfuric acid or some other condensing reagents (Bayer condensation, see Scheme 2 and ref 10). Generally, an excess of the less expensive chlorobenzene 2138
ENVIRONMENTAL SCIENCE &TECHNOLOGY / VOL. 29, NO. 8.1995
is chosen to bring the reaction to completion with respect to chloral. One reference lists reaction temperatures between 0 and 30 "C and durations up to 8 h (10). It was our hypothesis that an excess of chlorobenzene under certain conditions could lead to further substitution (replacement of the CCIBgroup in DDT by chlorophenyl) and formation of TCPM. Among the condensing reagents listed in one reference is anhydrous AlCb (11). DDT was one of the most important pesticides used in agriculture, forestry, and public health. Although its production has been stopped in most industrialized countries, DDT apparently is still produced in developing countries. The presence of TCPM as an impurity in technical DDT or its wastes would account as a probable source for environmental TCPM, and thus TCPM-OH, because of (a)the verylarge production volumes of technical DDT (cumulative world production in excess of 1 000 000 t), (b) its broad use pattern resulting in a nonpoint source, which would account for the global distribution of TCPM, and (c) its long-time production (since the 1940s), which accounts for the early presence of TCPM-OH such as in beluga whale and in harp seal fat collected in 1952 (see ref 3). The major metabolites of DDT in the environment are DDE, DDD, and bis(4-chloropheny1)aceticacid (DDA) (12, 13). Metabolic actions apparently are easier attacking the CC13 group than the phenyl rings in DDT. This would suggest that TCPM is more resistant to metabolism than DDT. Thus, the ratio TCPM/DDT could be considerably higher in environmental biological samples than in technical DDT. From metabolic studies of 2,4'-DDT in mammals, it was shown that metabolic attack was primarily at the the 2-chloro ring whereas the 4-chloro ring remained intact (14,15). From this fact, it can be speculated that 2,4'-DDT is less resistant to metabolism than 4,4'-DDT and may explainwhy2,4'-DDTis less abundant in biologicalsamples,
particularily in warm-blooded organisms, than expected from its presence in technical DDT. These considerations would suggest that 4,4’,4“-TCPM is more resistant to metabolism than the other TCPM isomers and thus could explain why this isomer is the only one present in environmental biological samples, particularly at higher trophic levels. However, 2,4‘-DDT has been detected at sigmficantlevels in fish (16,17)and these may be the species where other TCPM isomers might be expected. In fact, the likely presence of a second, earlier-eluting TCPM (and TCPM-OH) isomer has now been reported in fish but not in seal and in human milk (4). This would suggest that the second isomer is less resistant to metabolism such as expected for the 2,4‘,4”-companionof 4,4’,4”-TCPM in DDT. Environmental TCPM-OH was previously identified as the 4,4’,4”-isomer (1-3), but the isomerism of environmental TCPM was so far unknown though assumed to be the same. In this study, environmental TCPM has now been confirmed as the 4,4’,4”-isomer. The finding of the same isomerism for both compounds, their usual cooccurrence in all environmental and biological samples, and the likely presence of a second, earlier-elutingisomer for both of the compounds in fish is strong evidence that the two compounds result fromthe same source as pointed out previously (4). Small amounts of a contaminant or byproduct in a technical material such as DDT can still lead to detectable concentrations in environmental samples such as is the case with minor components of chlordane or toxaphene (18). It is presently impossible to estimate the concentrations of TCPM required in technical DDT to account for the TCPM levels in the environmental samples. Further analyses of technical DDT, from a wide range of manufacturers and from different manufacturing processes, will be required to establish whether this source is the major one for environmental TCPM or whether there must be additional sources.
Acknowledgments I wish to thank C. Rappe and D. Zook, Institute of Environmental Chemistry, University of Umel, Umel, Sweden, for making the seal extract available for analysis
and to M. D. Miiller, Swiss Federal Research Station, W&denswil,Switzerland,for detailed discussionsand review of the manuscript.
Literature Cited (1) Walker, W., 11; Risebrough, R. W.; Jarman, W. M.; de Lappe, B. W.; Tefft, J. A.; DeLong, R. L. Chemosphere 1989,18,1799- 1804. (2) Zook, D. R.; Buser, H. R.; Bergqvist, P. A.; Rappe, C.; Olsson, M. Ambio 1992, 21, 557-560. (3) Jarman, W. M.; Simon, M.; Norstrom, R. J.; Burns, S. A.; Bacon, C. A.; Simoneit, B. R. T.; Risebrough, R. W. Enuiron. Sci. Technol. 1992,26, 1770-1774. (4) Rahman, M. S.; Montanarella, L.; Johansson, B.; Larsen, B. R.
Chemosphere 1993, 27, 1487-1497. (5) Buser, H. R.; Mtiller, M. D. Anal. Chem., in press. (6) Mtiller, P. DDT, The Insecticide Dichlorodiphenylm’chloroethane andlts Significance; Birkhauser Verlag: Basel, Switzerland, 1955; VOl. 1. (7) Eliel, E. L.; Wilen, S. H. Stereochemistry of Organic Compounds; John Wiley and Sons: New York, 1994; p 1156. (8) Damico, 1. N. Pesticides. In Biochemical Applications of Mass Spectrometry; Waller, G. R., Ed.; Wiley-Interscience: New York, 1972; p 645. (9) Fieser, L. F.; Fieser, M. Lehrbuch der Organischen Chemie;Verlag Chemie: Weinheim, Germany, 1957; pp 639-642. (10) Sittig, M. Pesticide Manufacturing and Toxic Materials Control Encyclopedia; Noyes Data Corporation: Park Ridge, NJ, 1980. (1 1) Melnikov,N. H. Halogen Derivatives of Aromatic Hydrocarbons. In Residue Reviews; Gunther, F. A., Gunther, J. A., Eds.; Springer Verlag: Berlin, Germany, 1971; Vol. 36, Chapter VI. (12) Aizawa, H. Metabolic Maps of Pesticides;Academic Press: New York, 1982; p 39. (13) Kujawa, M.; Macholz, R. M.; Engst, R. Die Nahrung 1984, 28, 1065- 1080. (14) Feil, V. J.; Lamoureux, C. J. H.; Styrvoky, E.; Zaylskie, R. G. J. Agric. Food Chem. 1975, 23, 382-388. (15) Feil,V.J.;Lamoureux,C.J.H.;Styrvoky,E.;Zaylskie,R.G.;Thacker, E. J.; Holman, G. M. J. Agric. Food Chem. 1973,21, 1072-1078. (16) Ballschmiter, K.; Buchert, H.; Bihler, S.; Zell, M. Fresenius Z. Anal. Chem. 1981, 306, 323-339. (17) Muir, D. C. G.; Norstrom, R. J.; Simon, M. Enuiron. Sci. Technol. 1988, 22, 1071-1079. (18) Buser, H. R.; Muller, M. D.; Rappe, C. Enuiron. Sci. Technol. 1992, 26, 1533-1540. Received for review March 21, 1995. Revised manuscript received April 21, 1995. Accepted April 22, 1995.@
ES950182A @Abstractpublished in Advance ACS Abstracts, June 1, 1995.
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